Printing press with sheet turnover mechanism

ABSTRACT

Multicolor sheet fed printing press capable of printing sheets on one side only or perfecting on opposite sides. A sheet transfer unit between adjacent printing units takes advantage of a standard transfer cylinder and gripper and gripper cam arrangement when printing sheets on one side by providing for sheet movement along a first path, and may be arranged to alternatively transfer sheets along a second path between adjacent printing units while utilizing a sheet turnover system when perfecting. Adjustment for sheet length in the turnover system is effected by adjusting turnover cylinder means about cooperating cylinders to change the operating phase of a cylinder with tail grippers with respect to the cylinder from which the tail grippers take a sheet. Retiming of printing units is avoidable when changing from one-side printing to perfecting, and vice versa.

United States Patent [191 Ruetschle [451 May 20, 1975 PRINTING PRESS WITH SHEET TURNOVER MECHANISM [75] Inventor: Rudolph H. Ruetschle, Solon, Ohio 22 Filed: Jan. 20, 1972 21 Appl. No.: 219,273

[56] References Cited UNITED STATES PATENTS 357,927 2/1887 Hawkins 101/230 452,933 5/1891 Feister 101/230 X 666,325 1/1901 North 101/230 1,949,001 2/1934 Albrecht 101/230 2,757,610 8/1956 Gegenheimer et al 101/183 2,896,535 7/1959 Schunemann 101/152 3,537,391 11/1970 Mowry 101/183 FOREIGN PATENTS OR APPLICATIONS 82,935 7/1971 East Germany 101/230 494,311 9/1919 France 101/229 Primary Examiner-J. Reed Fisher [57] ABSTRACT Multicolor sheet fed printing press capable of printing sheets on one side only or perfecting on opposite sides. A sheet transfer unit between adjacent printing units takes advantage of a standard transfer cylinder and gripper and gripper cam arrangement when printing sheets on one side by providing for sheet movement along a first path, and may be arranged to alternatively transfer sheets along a second path between adjacent printing units while utilizing a sheet turnover system when perfecting. Adjustment for sheet length in the turnover system is effected by adjusting turnover cylinder means about cooperating cylinders to change the operating phase of a cylinder with tail grippers with respect to the cylinder from which the tail grippers take a sheet. Retiming of printing units is avoidable when changing from one-side printing to perfecting, and vice versa.

35 Claims, 11 Drawing Figures P TJENTEB HAY 2 0 IBYS SHEET 3 3? 6 FATENTED W 20 SHEET 5 BF 6 PRINTING PRESS WITH SHEET TURNOVER MECHANISM BACKGROUND OF THE INVENTION The invention relates primarily to a sheet fed printing press which is capable of printing sheets on opposite sides and particularly to one capable of being alternatively arranged to print sheets of various lengths either on one side only or to perfect by printing on opposite sides at adjacent printing units. An example of a machine capable of printing on the same side or opposite side in successive units is shown in U.S. Pat. No. 2,757,610, issued to H. W. Gegenheimer on Aug. 7, 1956. In the Gegenheimer patent, three transfer cylinders are arranged between two impression cylinders of a pair of adjacent printing units. When printing sheets on one side, the sheets are passed from a first impression cylinder to the second by means of sheet grippers on each of the three transfer cylinders. When printing on one side only, a first edge of each sheet which is leading in the first printing unit continues to be the edge by which the sheet is gripped and ultimately transferred to the grippers of the second impression cylinder. When the press is arranged to perfect by printing sheets on opposite sides at the two printing units, sheets travel around the second of the three transfer cylinders with their lead edges bypassing the normal transfer point between the second and third cylinders. After the bypass, special tumbler-type grippers on the third transfer cylinder are arranged to grip the tail edge of each sheet on the second transfer cylinder at the trans fer point. At the time the tail edge is gripped, the second cylinder releases its grip on the lead edge. After gripping the tail of the sheet, the tumbler-type tail edge grippers pivot in an arc in order to transfer the sheet to a second set of previously-pivoted grippers on the third transfer cylinder, thereby turning the sheet end for end so as to make the former trailing edge of the sheet become the leading edge for subsequent transfer to the grippers of the second transfer cylinder. Because of the unusual tumbling and sheet transfer action required of the two sets of grippers on the third transfer cylinder, their operating mechanisms are relatively complex in comparison to the normal gripper operating mechanisms utilized on the standard non-perfecting sheet fed printing presses. In the Gegenheimer construction, one set of the tumbler-type grippers also handles sheets during one-side printing. In addition to this, the presentation of the tail edges of sheets from the first set of grippers to the second set on the third transfer cylinder results in a dropping back of the turned-over sheet by a distance on the periphery of the cylinder equal to the spacing between the two sets of tumbler grippers. This and the increased sheet path due to gripping the sheet of the tail results in a phase change between the first and second printing units as compared to that when printing sheets on one side only. As described in the Gegenheimer patent, various things must be done to the mechanism and the relationship of the parts in order to compensate for this phase change when changing from printing one side to perfecting, and vice versa, as well as when changing sheet length during perfecting.

SUMMARY OF THE INVENTION According to one aspect of the present invention, sheets may be conveyed from a first printing unit,

where the sheet is printed on an obverse as it is conveyed through the unit with a first edge leading, to a second unit by traveling along a first path with the first edge leading the second so that it will be printed on the obverse side or it may be directed along a second path in its travel between units in which it is turned over end for end by cylinder and gripper means in the second path which continuously rotate in given respective directions for presentation to the second printing unit for printing on thereverse, i.e. opposite, side to that printed in the first unit.

Another aspect of the invention is the provision of a first sheet transfer path along which sheets are conveyed froma first printing unit to a first transfer nip at the impression cylinder of a second printing unit when the same sides of the sheets are to be printed by the units and of a second path along which the sheets may be conveyed when traveling between the units and in which the sheets are turned over for printing on the opposite side at the second unit and are presented to the impression cylinder of the second unit at a second transfer nip different from the first.

Another aspect of the present invention is the arrangement of cylinders in a sheet path where the sheet is to be turned over by gripping the tail of the sheet while it is being conveyed with a first edge leading in which the cylinders include a turnover cylinder for gripping the tail edge of a sheet being conveyed on a cooperating cylinder by its lead edge and the cylinders may be rephased to accommodate different length sheets by moving the turnover cylinder angularly about an adjacent cylinder.

A further aspect of the invention provides a sheet turnover path between units in which cooperating cylinders are translated bodilyrelative to each other to adjust transfer nips to compensate for changes in timing caused by gripping sheets by their trailing edge when effecting a sheet transfer at a sheet transfer nip in the path for different length sheets. This avoids a retiming of the units. Preferably the transfer nips are changed with the adjustment to effect the rephasing of a sheet handling cylinder in the path which conveys the sheet by gripping its leading edge with respect to a cooperating turnover cylinder which grips the trailing edge of a sheet to take the sheet from the sheet handling cylinder. To adjust the phasing between the turnover cylinder and the cylinder from which it takes a sheet, at least one of the cylinders is supported for angular movement about an adjacent cylinder to effect a relative rotation between the sheet handling and turnover cylinders to rephase the cylinders. Preferably, a four bar linkage supports this cylinder and one of its adjacent cooperating cylinders in the sheet path for movement as a unit about respective cylinders which form sheet transfer nips with the cylinders supported by the linkage. The linkage is also preferably connected to adjust the position of the gripper operating cams for effecting gripper operation at the sheet transfer nips for the cylinders being adjusted.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side elevational view of a convertible perfector and one side printing press, illustrating sheet travel along a first path in which sheets are printed on the same sides at two adjacent printing units.

FIG. 2 is a view of the printing press of FIG. 1 arranged to perfect sheets by printing on opposite sides at adjacent units, and illustrates a second path along which sheets travel when perfecting.

FIG. 3 is a view similar to FIG. 2 in which shorter sheets are perfected, and illustrates a repositioning of certain of the cylinders to accommodate such shorter sheets.

FIG. 4 is a view with the cylinders in similar positions to that in FIG. 1, illustrating certain operating mechanism of the invention.

FIG. 5 is a cross-sectional view of one type of mechanism for operating the grippers on certain of the press cylinders.

FIG. 6 is a view illustrating a means for automatically retiming one of the gripper-operating cams in response to repositioning of the cylinder on which it is mounted.

FIG. 7 illustrates the cams for operating one set of tail edge grippers on the turnover cylinder, on a larger scale.

FIG. 8 illustrates the cams for operating the other set of grippers on the turnover cylinder.

FIG. 9 is an enlarged view of the sheet gripper on the turnover cylinder.

FIG. 10 is a schematic side elevation of a modified form of printing press embodying the invention.

FIG. 11 is still another modified version of printing press embodying only certain aspects of the invention.

The present invention is an improvement on the basic concept of Robert K. Norton who conceived an off-line arrangement in which the sheet is intercepted from its path for same side printing by a first cylinder and then gripped by the tail while on the first cylinder to turn the sheet over. In the apparatus conceived by Norton, the sheet tail was to be gripped by tail grippers mounted on an indexable cylinder which moves the tail grippers in a direction opposite to sheet movement when the grippers are approaching and leaving the transfer nip but which is stopped and preferably reversed to move in the same direction as the sheet tail so as to be better able to grip the sheet tail. The described concepts of Norton are claimed by Robert K. Norton in an application Ser. No. 219,261, now abandoned, filed concurrently herewith and assigned to the same assignee as the present invention.

Referring now to FIG. 1, a pair of adjacent printing units 10 and 11 are arranged to print on the same side of sheets S passing therethrough. The first printing unit 10 includes an impression cylinder 12, a blanket cylinder 12 and a plate cylinder 14, which together form the three cylinders of a conventional offset printing unit. It should be understood, however, that the concept disclosed herein may be utilized with any type of printing press, the offset units being merely illustrative. As shown, cylinders 12, 13 and 14 are of the same diameter for convenience of an infeed (not shown) to cylinder 12. The impression cylinder 12 may, and preferably is in the case where unit 10 is the second or subsequent color unit of a multicolor press, be twice the diameter of the cylinders 13, 14 of the printing unit 10.

The second printing unit 11 includes an impression cylinder 16, a blanket cylinder 17 and a plate cylinder 18. Impression cylinder 16 is preferably twice the diameter of the other cylinders of that printing unit, and has two sets of grippers 19 which are spaced 180 apart. Between the impression cylinders 12 and 16 there is located a conventional transfer cylinder 20, which has grippers 21 which receive sheets from the grippers of the impression cylinder 12, and transfer them to the grippers on the impression cylinder 16. A cylinder 22 having grippers 23 is located to receive printed sheets from grippers 19 of the impression cylinder 16 for delivery or transfer to another printing unit.

All of the grippers 15, 21, 19 and 23 and their operating cams, (which will be discussed subsequently), are generally conventional grippers and cams of a sheetfed printing press. As such, the grippers are normally a plurality of fingers mounted on a gripper shaft extending fully across the cylinders.

FIG. 1 includes a simplified showing of such conventional grippers with respect to one set of grippers 21 for cylinder 20. The grippers 21 comprise a lever 24 which extends from a rotatable gripper shaft 25 which supports the fingers 25a and is rockable to open and close the fingers. A pair of side-by-side cam followers 26 (see FIG. 5) are arranged to ride on the surface of cams which will be discussed later in FIG. 4. A spring 27 is connected to the lever 24 to maintain the cam followers 26 in contact with the operative surfaces of the cams. The gripper fingers thus far described in connection with cylinders 12, 20, 16 and 22 are customarily referred to as positively closed, i.e. the cam followers 26 are intended to ride on the high lobes of the cams to urge the gripper fingers closed against sheets, whereas, when the cam followers are permitted to go to the low lobes of the cams, the springs 27 urge the gripper fingers to their open condition. Such positively closed grippers are considered in the art to provide the best gripper action on sheets for maintaining sheet register. The gripper fingers of adjacent sheet handling cylinders are conventionally adapted to transfer sheets at the line between centers of the two cylinders.

What has thus far been described in FIG. 1 is a standard multicolor sheet fed press adapted to print sheets on one side only at a pair of adjacent printing units. Only two such printing units will be described herein, since the sheet transfer unit described hereinafter between the printing units 10, 11 can be placed anywhere in a multicolor press. The sheet transfer unit may also be placed after the very last printing unit, just before the conventional sheet delivery, so that sheets can be delivered to a pile with the printed side either up or down when printing on one side only, or, when perfecting, either side can be located up or down as desired.

When printing sheets on opposite sides at the two printing units 10 and 11, i.e. on the obverse side at the printing unit 10 and the reverse side at unit 11, which is commonly referred to as perfecting, the sheets are arranged to be turned over and end for end by an auxiliary sheet transfer unit which includes a cylinder 28 and a turnover cylinder 29. Generally speaking, the diverting cylinder 28 is preferably a double size transfer cylinder having two sets of lead edge grippers 30 and preferably a plurality of tail edge grippers preferably in the form of vacuum shoes or suckers 31 for each of the lead edge grippers. The vacuum shoes are preferably movable either independently or in unison in circumferential, axially spaced slots indicated by dotted lined in the periphery of cylinder 28 (see FIG. 2) for purposes of adjustment and for sheet tensioning purposes. The cylinder 28 may be of the same skeletonal type shown in the Gegenheimer patent. The shoes are arranged to grip the tail edge of each sheet at the line between centers of the transfer cylinder 20 and the diverting cylinder 28. They then preferably move a small amount to tension the sheet about the periphery of cylinder 28 prior to its tail edge being transferred to special tumbler-type grippers on the turnover cylinder 29. The vacuum shoes may be of the type illustrated in U.S. Pat. Nos. 3,430,946 and 3,096,088 to Carl 0. Siebke and William G. Young, respectively.

The press is adapted to print sheets of various lengths, and the vacuum shoes 31 are adjustable to various locations as disclosed in the aforesaid patents to grip the tails of sheets anywhere between the normal maximum and minimum length sheets to be handled by the press. Reference may be made to FIGS. 2 and 3 which illustrate respectively the maximum length and minimum length sheet perfecting respectively, and the relationship of the vacuum shoes 31 to the grippers 30 for each case can be seen by reference to those figures.

The turnover cylinder 29 includes two sets of grippers 32 and 33 disposed adjacent the opposite edge of an axially extending gap 29a in the cylinder periphery. The tail edge gripper 32 is adapted to grab the tail of sheets from the vacuum shoes 31, and grippers 33 are adapted to receive sheets from the grippers 32 and subsequently pass them to the grippers 19 of the impression cylinder 16 at the line between centers of cylinders 29 and 16. Again, this mechanism may be substantially similar to that shown in the aforementioned Gegenheimer patent, but, if desired, may be but a single set of grippers which takes the tail of the sheet from the tensioning cylinder 28 while positioned adjacent one edge of the gap 29a and then tumbles through approximately 180 to position the gripped edge of the sheet adjacent the other edge for transfer of the sheet to the grippers 19 of the impression cylinder 16.

Diverting cylinder 28 is adapted to be adjusted in an arcuate path about the fixed axis 34 of the transfer cylinder 20, and turnover cylinder 29 is adapted to be similarly adjusted about the fixed axis 35 of impression cylinder 16. The limits of their adjustments are labeled as minimum and maximum positions in FIG. 1. The purpose of a range of adjustments is to accommodate sheets of different lengths when perfecting by changing the distance along the cylinder 28 between the grippers 30 from the transfer point for the tail edge of the sheet to the turnover cylinder 29 when the grippers 32 of cylinder 29 are in position to take the trailing edge. The mechanism is capable of infinite adjustment between these limits.

It will be seen from FIG. 1 that sheets printed on one side only pass through the press without being handled whatsoever by diverting cylinder 28 or turnover cylinder 29. As mentioned previously, this enables use of standard grippers and gripper-operating components known for capably and accurately maintaining sheet register throughout the press. The cylinders 28 and 29 may be considered as being off-line cylinders, since they only come into play when sheets are perfected. They perform no sheet handling function during oneside printing. As will be seen, the mechanisms necessary to effect the turnover of sheets end for end is relatively complex, in comparison, has many parts capable of wear, and must go through considerably more difficult operations to perform their necessary functions. While some such mechanisms are capable of performing to a reasonably high standard of printing, they do not ordinarily meet the exacting requirements of top grade registration such as required in highest quality printing. One particular presently known difficulty is the difficulty of designing such tumbler grippers for positive closing action as discussed previously in connection with those grippers utilized when printing sheets on one side only.

When perfecting, however, the printing performed by the unit 11 is placed on the reverse side of the sheet that printed at unit 10, therefore registration is from one side of the sheet to the other, rather than of two colors on the same side of the sheet. So long as the cylinders 28 and 29 are capable of good print repeatability, registration from one side of the sheet to the opposite side need not compare to the much greater accuracy required when printing two colors on the same side, although the repeatability is required to avoid a printing problem known as doubling off the second impression cylinder. When printing two colors on the same side at units 10 and 11, as mentioned earlier, the sheets are handled only by grippers and gripperoperating mechanisms which do not need to be moved to reposition the edge of the sheet after gripping and the print register therefore can be held to known and accepted closely-held tolerances with conventional grippers.

Sheets which pass around the impression cylinder 12, the transfer cylinder 20, the impression cylinder 16 and the transfer cylinder 22 are hereinafter referred to as traveling along a first path. For all practical purposes, this refers to the fact that the same edges of sheets S are maintained as the leading edges in their complete movement from the printing nip between the impression cylinder 12 and blanket cylinder 13 on one handat the first unit 10, and the impression cylinder 16 and the blanket cylinder 17 on the other hand at the second unit 11.

When sheets are to be perfected, they are arranged to be intercepted or diverted from the first path, carried along a second path in which they are turned over end for end, and returned to the first path at a point downstream from the point at which they were intercepted. This second path is independent of the first path, in that sheets are completely removed from the first path while they are turned over end or end, and before they are returned to the first path. This enables some important advantages in press design and operation, over and above the already-mentioned advantage that only standard gripper and gripper-operated mechanisms are utilized for one-side printing. A first important advantage is that the phase relationship between the printing units 10 and 11 need not be changed when converting to perfecting. Also, it enables adjustments to be made in the second path which do not affect the first path and which are such that the phasing of the units need not be changed to accommodate different sheet lengths. This simplifies makeready techniques to be performed when converting from one-side printing to perfecting, or vice versa, or when merely changing sheet length when perfecting. It will be noted that in the aforesaid patents the gripping of a tail of a sheet when perfecting effectively adds to the sheet path between the impression cylinders of the units by at least the length of the sheet as well as by the drop back on tail grippers on the turnover cylinder. This means that the second printing unit of the aforesaid patents must be retimed to adjust for the change in sheet path. By placing cylinders 28 and 29 off-line, so that the second path is independent of the first path, however, the sheets may be returned to the first path in a manner in which no change in timing is necessary because of the increased travel on the perfecting changeover or because of the drop back of the tail gripper. In addition, by adjustably positioning the transfers between the second path and design advantages for any electrically or electronically-controlled press by avoiding the necessity of compensating for time changes for each different length sheet perfected, this would simplify the electronic controls over comparable controls which might be utilized by the Gegenheimer structure.

Referring specifically now to FIG. 2, illustrated therein is the perfecting unit for turning sheets over end for end, the sheets shown in this Figure being of the maximum length capable of being handled by the press. Sheets S taken from the impression cylinder 12 by the grippers 21 of transfer cylinder are transferred to grippers of diverting cylinder 28 at a transfer point along the lines between centers of the transfer cylinder 20 and the diverting cylinder 28. This transfer point is generally referred to herein as the point of interception or diverting of sheets from the first path. A sheet tensioned by the vacuum shoes 31 on the periphery of the cylinder 28 is taken by the grippers 32, and simultaneously, the grippers 30 open to release the lead edge of the sheet as illustrated at the bottom of FIG. 2. Grippers 32, in their travel in a clockwise direction, transfer the tail edge of the sheet S to grippers 33, and grippers 33 now tumble to a position to make the former tail edge of the sheet become the leading edge, so that it can be transferred to the gripper fingers 19 on impression cylinder 16. At the point where the grippers 19 are at the line between centers of cylinders 16 and 20, it may be considered that the sheets which have been turned over end for end have now been returned to the first path. The second path may therefore be considered as being the sheet travel from the point of receipt of sheets by the grippers 30 of cylinder 28 to the point where grippers 19 reach the line between centers of the impression cylinder 16 and transfer cylinder 20. It will be seen that the sheets which have been turned over end for end have been completely removed from the first path during the turnover process.

FIG. 3 is a view similar to FIG. 2 in which minimumsize sheets are perfected. It will be seen that the sheets S extend a much smaller distance around their respective cylinders, and the cylinders 28 and 29 are located leftwardly of their FIG. 2 position. The principal gripper-operating cams for grippers on the cylinders, and also the mechanism for positioning the cylinders 28 and 29 between their minimum and maximum positions are illustrated in FIG. 4. For purposes of clarity of viewing the parts, the grippers on the various cylinders have been purposely omitted, and the various drive gears, one on the end of each cylinder, for driving the cylinders are merely shown as dot-dash lines at their points of mesh. It can be seen from the dot-dash lines, that there is gear mesh between cylinders 12 and 20, 20 and 16, 16 and 22, 20 and 28, and 16 and 29. The drive gear for each cylinder is fixed to the respective cylinder and has a pitch diameter corresponding to the diameter of the cylinder. There is no gear mesh, however, between cylinders 28 and 29. Since all of these gears are arranged to have their pitch line at the circumference of the respective cylinders, it is obvious that the two gears on the cylinders 28 and 29 should be laterally offset in any conventional fashion to avoid meshing.

When printing sheets on one side only, as is illustrated in FIG. 1, the sheets travel in their first path around cylinders 12, 20, 16 and 22. The gripper fingers 21 on transfer cylinder 20 are arranged to be operated by a conventional cam 36 and to open to receive sheets from the gripper fingers 15-of cylinder 12. They then close and are kept closed by cam 36 and an adjustable cam 37 until the sheets are finally transferred to grippers 19 on impression cylinder 16, after which grippers 21 immediately open. Cam 36 is mounted in fixed position in the printing press and is arranged to operate the grippers 21 on transfer cylinder 20 to close on sheets at the line between centers of cylinders 12 and 20. Cam 37 is adjustable between its full-line position in which it is locked relative to cam 36 by any known means when printing one side, and a position in which it is arranged during perfecting to open the grippers 21 on transfer cylinder 20 at the transfer point along the line between centers of the transfer and diverting cylinders 20 and 28 to release sheets to grippers 30 on the diverting cylinder. The cam 37 is adjusted so that the overlap of the high dwell of the cams 36 and 37 controls the point of opening of grippers on the transfer cylinder 20 so as to selectively maintain the grippers positively closed from the point of receipt of sheets from the cylinder 12 either to the point of transfer from the cylinder 20 to the cylinder 16 when printing on one side, or when perfecting, from the cylinder 20 to the cylinder 28. To release the grippers at cylinder 28 in FIG. 4, the cam 37 is adjusted counterclockwise as viewed in FIG. 4 to the position the cam 37 with its release slope 37a immediately adjacent the transfer nip between transfer cylinder 20 and diverting cylinder 28.

The grippers 19 on impression cylinder 16 of the second unit are operated solely by a conventional positive closing cam 38 when printing sheets traveling along the first path. When perfecting, an adjustable cam 39 is arranged in the solid line position of FIG. 4 to cause the grippers 19 to close on sheets as they are received from the grippers 33 on the turnover cylinder 29. When printing on one side, the cam 39 is locked to the cam 38 in the dot-dash line position shown, so that its effective high dwell periphery is coincident with the high dwell of the cam 38. Cam 39 is thus utilized only for perfecting. The cam followers on the impression cylinder l6 and transfer cylinder 20 are generally constructed as shown in FIG. 5, wherein the gripper shafts 25 carry a pair of side-by-side cam followers 26a and 26b which are adapted to cooperate with cams 36 and 37 (or 38 and 39) respectively. By cross-referring to FIG. 4, cam follower 26a will ride on the high dwell of cam 36 from the point of receipt of sheets from the impression cylinder 12 until the grippers 21 are just short of the line between centers of cylinders 20 and 28. At that time, however, the cam follower 26b will already be on the high dwell of cam 37, such that the gripper fingers 21 are maintained closed to carry the sheets all the way to the point of transfer between the cylinders 20 and 16. At the point of transfer to impression cylinder 16, both rollers 26a and 26b are permitted to drop to the low dwell of earns 36 and 37 to cause the gripper shaft 25 to be pivoted to a position in which the gripper fingers open and permit transfer of sheets to grippers 19 of the impression cylinder 16. Cam followers similar to 26a and 26b are utilized to cooperate with the cams 38 and 39 of the impression cylinder 16.

Referring to FIG. 4, the cylinders 28, 29 are supported from the cylinders 20 and 16 by means of a first pair of links comprising links 40, 40' (only one of which is shown in FIG. 4) and a second pair of links comprising links 41, 41', respectively. In this manner the shafts 42 and 43 of cylinders 28 and 29 have their axes maintained parallel with respect to the shafts of the transfer cylinder and impression 16 for all positions of adjustment of the links 40 and 41. In addition to these links, a third pair of links comprising links 44, 44' (see FIGS. 7 and 8) is provided to maintain the distance between the axes of the shafts 42 and 43 constant for the various positions of adjustment of the cylinders 28 and 29. Together, the first, second and third links, along with the fixed axes 34 and 35 of the impression and transfer cylinders 16 and'20 constitute a four-bar linkage which enables the arcuate adjustment of the cylinder 28 with respect to the cylinder 20 and of the cylinder 29 with respect to the cylinder 16 as mentioned previously. In addition, links 44, 40' constantly maintain the distance between the axes of the cylinders 28 and 29 so that their surfaces are always in the same spatial relationship. If desired, arcuate slots may be provided in the usual side frames of the press in place of the links 40, 40', 41, 41'. The shafts 42 and 43 may ride in the slots to give the same movement as it provided by the pairs of links 40, 40' and 41, 41. In such a case, additional means to perform the function of links 44, 44 to maintain the distance between the shafts 42 and 43 would also be required, although links .44, 44' may also be used in conjunction with slots. The

pairs of links 40, 40 and 41, 41' are preferable, however, because these links can be made to support cam mechanisms for operating the grippers of cylinders 28, 29 when perfecting, and when these links are moved to their various locations for changing sheet length, the cams will move with the links and always maintain the transfer points between the various cylinders in the same relationship for all of the various positions of the cylinders 28 and 29.

Repositioning of cylinders 28 and 29 may be accomplished by any of a variety of means which can be provided by those skilled in the art recognizing that such means are to be locked after adjustment to maintain the cylinders in their new positions. An example of one such adjusting means is illustrated as a crank 45 which turns one of a pair of bevel gears 46 and 47, the latter of which rotates a worm 48 journaled in framework of the press. Rotation of the worm 48 in response to the turning of the handle 45 operates a worm gear 49 to rotate a shaft 50. The shaft 50 extends the full length of cylinder 28. A pair of levers 51 only are being shown in FIG. 4 and are mounted on opposite ends of the shaft 50. Each of the levers 51 has connected to the extended end thereofa link 52 which is connected at its other end to the adjacent end of shaft 42 of the diverting cylinder 28. In the form illustrated, the use of a selflocking worm and worm gear arrangement will lock the cylinders in their final adjusted position.

Thus far the function of earns 36, 37, 38 and 39 in connection with printing sheets on one side only when they are traveling along the first path has been described. When converting from one-side printing to perfecting, the preferred embodiment of the invention requires making the following changes. Cam 37 should be unlocked from fixed cam 36 and fastened to the link 40 at that side of the press. This may be done by simply bolting the cam to the link with the bolt holes in the link (see FIG. 5) properly locating the cam 37 to release the sheets at the nip between transfer and diverting cylinders 20, 28. Other suitable means for connecting the cam 37 to the link 40 is entirely within the ability of those skilled in the art. The slope on cam 37 where the cam follower 26b rides from the high dwell to the low dwell is arranged to be after the line between centers of cylinders 20 and 28 and is such that the grippers 21 effect release of the sheets to grippers 30 directly at the line between centers. The location of this slope will vary relative to cam 36 according to the position of adjustment of the cylinders 28 and 29, although it will be adjusted to maintain a constant relationship to the linebetween centers when perfecting. The timing of opening of the grippers 21 on the transfer cylinder 20 will always occur on the line between centers. Similarly, cam 39 is connected to link 41 to be movable therewith to adjust the opening and closing of the grippers on the impression cylinder 16 of the second unit so that proper timing is maintained with the turnover cylinder 29 as it is adjusted about the axis of impression cylinder 16.

The grippers 30 on diverting cylinder 28 are operable to receive sheets from the transfer cylinder 20 by means of a short positive opening cam 53. The cam 53 is supported by the link 40 through an opening in a part 56. As the grippers 30 and their cam follower approach the cam 53 in a counterclockwise direction, they ride up on the high part of the cam 53 to open, and are adapted to close on sheets received from the transfer cylinder 20 as they ride down the slope of the cam 53 to the low side thereof. Thereafter, until they release the lead edges of sheets, they are maintained closed by their conventional springs (not shown). After the grippers 21 on the transfer cylinder 20 open to release sheets to the grippers 30 on the diverting cylinder 28, cam followers 26a and 26b ride on the low part of earns 37 and 36 so as to be maintained in their opened condition and avoid interference with the impression cylinder 16.

As the tail end of a sheet arrives at the transfer point between the cylinders 20 and 28, it is gripped by the vacuum shoes 31 which, as described in the aforementioned patents to Siebke and Young, have a tensioning motion opposite to the direction of rotation of the cylinder 28 to tauten the sheet on its periphery prior to the tail edge being gripped by grippers 32 of the turnover cylinder 29. After the sheet is gripped by the grippers 32, an adjustable cam 54 opens the lead edge grippers 30 on the turnover cylinder. This cam 54 is journaled on the shaft 42 of cylinder 28 and is adapted to pivot about the axis of the shaft whenever the cylinder 28 is adjusted to a new position.

The cam 54 is carried by a support member 55. The support member 55 includes an extension 56 which has at its end a gear sector 57 having a pitch diameter coincident with the pitch diameter of the gear on the cylinder 28. This gear sector, as shown in FIG. 6, meshes with a gear sector 58 fastened to a press frame and having teeth coincident with the drive gear on the cylinder 20. When the cylinder 28 is adjusted in its arcuate direction about the axis 34 of the transfer cylinder 20, the

sector 57 will rock about the teeth of fixed sector 58, thus angularly positioning the cam 54 automatically in response to the extent of movement of the links 40 so that the cam will always be effective to open the grippers 30 at the transfer point between cylinders 28, 29.

The grippers 32 and 33 on turnover cylinder 29 which receive the sheet from grippers 30 have a total of six gripper cams, three at each end of the cylinder. For sake of clarity, that mechanism will be described in conjunction with FIGS. 7 and 8 and at the same time related to their functions in connection with the mechanisms of FIGS. 4 and 9. On the side of the press facing the viewer in FIG. 4, three earns 59, 60, and 61 which perform the following functions are provided, and all of which are mounted in a fixed relation to link 44 so as to move with that link for the various positions of adjustment of the cylinders 28 and 29. Cam 59 is arranged to open and then close gripper fingers 32 onto the tail edges of sheets held by the vacuum shoes 31 just prior to the time of release by the grippers 30 of the diverting cylinder 28. The control for the vacuum shoes 31 is adapted to break vacuum, and preferably introduce air under pressure to the shoes at the time the grippers 32 receive the sheets, such control systems being described in the aforesaid patents.

The cam 60 is arranged to open the grippers 32 to release the sheets to the grippers 33 on turnover cylinder 29. Immediately prior to this opening, both grippers 32 and 33 have been tumbled, as is shown in dotted lines in FIG. 9, and grippers 33 close on the sheet S just before grippers 32 are opened by the cam 60. The grippers 32 are pivoted or tumbled from their full-line to dotted-line position in FIG. 9, to transfer the sheet gripped thereby to the grippers 33, by the cam 61 which pushes on a link 62 to operate a lever 63 to rotate a tumbling shaft 64 rotatable to tumble the grippers 32. Their tumbling action from the full to dottedline positions of grippers 32 in FIG. 9 occurred between sequential action by the cams 59 and 60 to respectively open the grippers to receive the sheet and to open the grippers to release the sheet.

At the opposite end of the cylinder 29 there is provided a cam 65 carried on link 44 and a pair of earns 66 and 67. Cam 66 is adapted to open grippers 33 to release sheets to grippers 19 of the impression cylinder 16, while cam 67 is arranged to tumble the grippers 33 from the dotted-line position of FIG. 9 to the full-line position of FIG. 9 prior to transfer of sheets to the impression cylinder 16. Cams 66 and 67 are fixed relatively to link 41' so as to maintain the timing of transfer of sheets and provide the necessary tumbling action at the proper times for all adjusted positions of the cylinder 29.

Referring back to FIG. 7 while cross-referring to FIG. 9, the grippers 32 are operated by a cam follower 68 carried on a lever connected to a gripper shaft 74 for the grippers 32. The follower 68 is first adapted to rise on the cam 59 to open the grippers preparatory to receiving the tail edge of the sheet. When the follower 68 rides off the cam 59, a spring 69 urges the gripper fingers 32 to closed condition to grip a sheet against gripper pads 70, one being provided for each of the plurality of gripper fingers 32. The pads 70 are mounted on a bar for rocking movement with the gripper finger on tumbler shaft 64 as an assembly, in response to movement of the link 62.

After gripping the tail of the sheet, the lever 63 is rocked in response to the riding of a cam follower 71 on cam 61. A spring 72 biases a rocker arm about a pivot shaft 73 to maintain the follower 71 in contact with the surface of the cam 61. As stated previously, this tumbling of shaft 64 occurs between the time that grippers 32 receive the tail of the sheet, and the time the sheet is transferred to the grippers 33. In the tumbled position, the cam follower for opening the grippers 32 will have moved to a new position in which it will now be aligned to engage the surface of cam 60, which surface faces inwardly of the cylinder 29. After the tumbling of the grippers 32, the follower 68 rides to the rise of cam 60 to rotate the shaft 74 to open the grippers. The grippers may again close immediately after passing off the operative portion of the cam 60, but by that time the grippers 33 and their corresponding gripper pads 75 have tumbled the sheet S out of the way of grippers 32 and their pads 70. It is to be understood from the foregoing that the grippers 33 are in position to receive the sheet when the grippers 32 are tumbled to their dotted-line position in FIG. 9. At any time thereafter according to design preferences, shaft 64 may again be tumbled by the cam 61 into position for the grippers 32 to receive sheets by their tails from the vacuum shoes 31.

Referring now to FIG. 8, the cylinder 29 is shown in a position just prior to the grippers 33 being tumbled inwardly under control of the cam 67 to the dotted-line position of FIG. 9. It will be seen that a cam follower 76 mounted on a crank arm 77 is just about to be biased by the spring 78 to the lowermost part of the cam 67. This spring 78 thus urges a link 79 to move a lever 80 in a clockwise direction to pivot the tumbler shaft 81 clockwise to tumble the grippers 33 and their pads 75 to the dotted-line position of FIG. 9 which is approximately 90 from the full-line position of FIG. 9. The entire gripper mechanism will retain that tumbled position until receipt of sheets from the gripper fingers 32. Prior to receipt of those sheets, however, the fingers 33 must be opened. This is accomplished by cam 65 carried on link 44, as it is engaged by a cam follower 82 which rotates the fingers 33 clockwise about the axis of a gripper shaft 83. When the mechanism has been tumbled inwardly to the dotted-line position of FIG. 9, cam follower 82 has a position located further inwardly of cylinder 29 on cam 67 As it rides onto the slope of cam 65, it begins to open and will be fully opened when riding on the high of the cam; The grippers 33 will close as they ride off the high of cam 65. This is the position they assume immediately after the time while both grippers 32 and 33 are simultaneously holding the tail edges of sheets. During the time this has occurred, the cam follower 76 will be riding on the low dwell of cam 67, maintaining the tumbled grippers 33 inwardly of the cylinder 29. This mechanism then tumbles outwardly, back to the full-line position of FIG. 9 as it rides up the slope of cam 67 to the outermost dwell position of tumble cam 67. At that time, it is in sheettransferring position for transferring a sheet to the impression cylinder 16. When in the full-line position as shown in FIG. 9, a cam follower 84, which is connected by a lever to the gripper shaft 83 for the grippers 33, engages the positive-opening cam 66. Cam 66 is arranged to commence release of the sheet as the follower 84 begins to ride up toward the high dwell of the cam, and is fully opened at the high dwell. As it rides down the opposite slope, a spring 86 returns the fingers 33 back to their closed position in which they are retained until again opened by engagement of the cam follower 82 with the cam 65.

It should be noted that the cams which operate the grippers, the timing of which must be changed with a relocation of the cylinders 28 and 29, are made to be adjusted with the cylinders by being carried on the links 40, 41, 41 44, and 44'. In this fashion, if perfecting is being accomplished on sheets of one length and a subsequent job is to be perfected on sheets of a different length, the basic step required to accomplish the change is to crank the mechanism by means of the handle 45 to reposition the cylinders and thier cams. This with a re-adjustment of the vacuum shoes on diverting cylinder 29 will accomplish the adjustment necessary for a change in sheet length. It will be noted that adjustment of the transfer and diverting cylinders 28 and 29 about the cylinders 20 and 16 respectively not only effects a change in the phase relationship of cylinders 28, 29 but also effects a translation of the sheet transfer nips between transfer and diverting cylinders 20 and 28 and between turnover cylinder 29 and impression cylinder 16 to compensate for the change in sheet travel which occurs on diverting cylinder 28 on a change in sheet length. For example, if a change to a shorter sheet is made, less angular rotation of the diverting cylinder 28 is required after receiving the lead edge at the transfer nip with the transfer cylinder 20 to position the tail edge of the sheet to be gripped by the tail edge grippers on the turnover cylinder. This earlier arrival of the tail at the grippers 32 would cause the sheet to arrive at the impression cylinder 16 too early except for the fact that the transfer nips between cylinders 20 and 16 are adjusted in location to compensate for this change. The movement of diverting cylinder 28 to adjust for a shorter sheet causes the diverting cylinder 28 to receive the sheet at a later time in the machine cycle when the impression cylinder 16 will have rotated so that the grippers are closer to the transfer nip with turnover cylinder 29. This latter nip will also be adjusted toward the oncoming grippers by movement of turnover cylinder 29 to further compensate for the shorter length and what would otherwise be a too early arrival of the sheet at the nip.

While adjustment of the vacuum is done separately in the illustrated embodiment, it will be understood that the shoes could be adjusted automatically with movement of the cylinders 28, 29 about the cylinders 20, 16 by using a stationary gear segment of the same pitch diameter as the cylinder drive gear and a cooperating gear on the cylinder axis and operating through a gear drive to shift the shoes as the cylinders are moved. The gear segment and cooperating gear would be finer gearing than the drive gears. The cooperating gear should be declutched from the gearing or otherwise disengaged when printing and the shoes locked in position by a brake or a self-locking gear drive.

Only when changing from one type of printing to the other is any other mechanical makeready required. When going from perfecting to one-side printing, cam 37 for operating grippers on transfer cylinder 20 is to be changed from its dot-dash line position in which it is connected to link 40, and placed in its full-line position as shown in FIG. 4. Cam 39 for operating grippers on impression cylinder 16 is to be removed from link 41 and placed in its dot-dash line position of FIG. 4 in which it is fixed to cam 38. Cam 53 for opening grippers 30 on diverting cylinder 28 is moved from its fullline position in an arcuate path to its dot-dash line position. The purpose of this latter movement is to make certain that the grippers 30 are maintained fully opened each time they arrive at the line between centers of cylinders 20 and 28, so as not to touch sheets when printing sheets are moving solely in the first path.

A substitute solution to accomplish the same end would be to have each of cylinders 28 and 29 declutched from their respective gears and mounted in a fixed position such that the gaps in cylinders 28 and 29 face the cylinders 20 and 16 respectively, so as to not have any parts interfere during one-side printing. In this latter situation, all of the mechanism of the diverting and tensioning cylinder 28 and turnover cylinder 29 would remain idle. This would reduce wear and tear on the mechanisms when not perfecting, and in addition would avoid the possibility that unnecessary machine vibrations might occur due to cam opening and closing in the unused perfector section of the transfer unit. When switching from one-side printing to perfecting, cams 37, 39, and 53 should be placed in their opposite conditions, the cylinders 28 and 29 should be properly positioned for the appropriate sheet length, and the press would then be ready to operate.

FIG. 10 illustrates one modification of the invention in which cylinders 101, 102 and 103 are impression, blanket and plate cylinders respectively of the first offset printing unit of a multicolor printing press. The impression cylinder 101 is shown as being double the diameter of the plate and blanket cylinders. A second printing unit includes an impression cylinder 104, a blanket cylinder 105 and a plate cylinder 106. The impression cylinders 101 and 104 are operably connected by means of a transfer cylinder 107 which is essentially comparable to the transfer cylinder 20 of the version of the invention described in FIGS. 1 through 9, insofar as it performs the function of transferring sheets directly from the impression cylinder 101 to cylinder 104 when printing sheets on one side only.

When perfecting, the sheets are transferred from cylinder 107 to a tensioning cylinder 108 and then to a tail turnover cylinder 109, and ultimately back to the transfer cylinder 107 by means of an auxiliary transfer cylinder 110. In this version of the invention, cylinder 108 has a fixed axis, whereas cylinders 109 and 110 are movable between their full and dotted-line positions to adjust for sheet length. Dot-dash and dot-dot-dash lines further illustrate the adjustment of the four-bar linkage mentioned previously. It is seen that the tensioning cylinder 108 need not be one of the cylinders moved when the timing adjustment is made. Cylinders 107 through 110 are interconnected by gears in similar fashion to that described previously in connection with FIG. 1 modification, except that there is no gear mesh at the nip between tensioning cylinder 108 and turnover cylinder 109. It is noted that sheets are intercepted from the transfer cylinder 107 and delivered directly back to the same transfer cylinder by the auxiliary transfer cylinder 110.

A further modification incorporating the off-line aspects of the invention is illustrated in FIG. 11. In this Figure, a first printing unit with an impression cylinder 201, a blanket cylinder 202, and a plate cylinder 203 is provided. The second printing unit of the press includes impression cylinder 204, blanket cylinder 205 and plate cylinder 206. Transfer cylinders 207, 208 and 209 between adjacent impression cylinders 201 and 204 maybe identical to and serve the exact same functions as those described in the aforementioned Gegenheimer patent. In that instance, cylinder 208 is a tensioning cylinder and cylinder 209 is the tail turnover cylinder. Sheets are gripped by their tails at the nip between the cylinders 208 and 209.

lt will be noted that cylinder 209 and its tumblingtype grippers are utilized in FIG. 11 version only when perfecting, and is off-line with respect to the remainder of the press when printing sheets'on one side at both units. Sheets to be printed on one side only are transferred from the impression cylinder 201 to cylinder 207, then around cylinder 208 to its point of transfer with a transfer cylinder 210, and then directly from transfer cylinder 210 to the impression cylinder 204 of the second printing unit. The grippers on tensioning cylinder 208 can be standard rather than the tumblingtype, since they only handle the lead edges of sheets. Thus, the version illustrated in FIG. 11 enables off-line perfecting and the utilization of standard grippers and gripper-operating mechanisms when printing sheets on one side. As shown in FIG. 11, however, the press is incapable of accomplishing the cylinder adjustment for sheet length purposes such as is illustrated in the earlier-described modifications. Rephasing of the first and second printing units is required for different sheet lengths when perfecting in the FIG. 11 modification.

In addition to the various modifications shown in the drawings, still others become apparent from the teaching herein. For example, the transfer cylinder of FIG. 1 can be replaced with three cylinders for one side printing and with two other cylinders off-line for perfecting, the latter two being adjustable and located either between the first and second or the second and third transfer cylinders.

Since all of the cams utilized during perfecting are mounted on the links which reposition the cylinders 28, and 29, it is possible for the four-bar linkage to be minutely adjusted during printing, in response to the detection of the position of the tail of the sheet as it is transferred to the cylinder 28. For example, let us assume a pile of sheets has been inaccurately cut, so that the length of one sheet to the next may vary a fraction of an inch. A sensor might detect this change in length, and effectively compensate for the slight change by automating the bevel gears 46 and 47 to compensate therefor. The time over which this could occur would be between the time the grippers 30 receive sheets from the grippers 21, to the time they release sheets in response to being opened by cam 54.

Various other modifications and changes may be made without departing from the spirit and the scope of the claims.

Having described my invention, I claim:

1. A multicolor sheet-fed printing press including first and second adjacent printing units providing first and second printing nips respectively, each unit comprising an impression cylinder with gripper fingers thereon, and sheet transfer means between the printing units for transferring sheets from the first unit to the second unit and selectively presenting the sheets to the second printing nips either with the same edge leading as was leading in the first printing nip whereby to print on the same sides of sheets at both units, or to turn sheets over and end for end whereby the tail edges of sheets leaving the first printing nip become the lead edges of sheets at the next unit in order to print on opposite sides of sheets at each unit,

2. A printing press according to claim 1 including means maintaining constant the distance between the axes of the diverting and turnover cylinders throughout their full range of adjustment.

3. A printing press according to claim 1 including a cam for opening the lead edge grippers on the diverting cylinder at the time sheets are taken by the tail edge grippers on the turnover cylinder, and means interconnecting said lead edge gripper cam for coordinated adjustment in response to arcuate adjustment of said turnover cylinder, whereby said cam is adapted to operate the lead edge grippers on the diverting cylinder to their opened condition when the tails of sheets held thereby are taken by the tail edge grippers, irrespective of the adjusted position of said diverting cylinder.

4. A printing press according to claim 3 wherein said diverting cylinder lead edge gripper cam is pivotally mounted with respect to the axis of the diverting cylinder, a first gear segment fixed relative to said cam, and a second gear segment fixed relative to said press and coaxial with said sheet handling cylinder of said first means, whereby arcuate adjustment of said diverting cylinder rocks said cam to a new position in response to meshing teeth of said first and second gear segments.

5. A printing press according to claim 1 wherein the meshing relationship of the gearing of the first means with the gears on the impression cylinders of the first and second printing units and the phase relationship of the respective cylinders are maintained intact throughout the full range of arcuate adjustment of said diverting and turnover cylinders.

6. A printing press according to claim 5 wherein said distance maintaining means comprises at least one link connected at its ends to said turnover and diverting cylinders at their respective axes.

7. A printing press according to claim 5 including first link means supporting said diverting cylinder for the arcuate adjustment about the axis of said cylinder of said first means, and second link means for supporting said turnover cylinder for the arcuate adjustment about the axis of the impression cylinder of the second printing unit.

8. A printing press according to claim 7 including third link means maintaining constant the distance be- 'tween the axes of the diverting and turnover cylinders,

said first, second and third link means together with the fixed axes for said cylinder of said first means and the impression cylinder of the second printing unit comprising a four-bar linkage.

9. A printing press according to claim 8 wherein means is provided for locking the four-bar linkage in a fixed position during operation of said press, and means interconnecting a fixed press member and said linkage for adjusting said linkage.

10. A printing press according to claim 7 including camming means for performing camming operations mounted on at least one of said first and second link means, and means for operating the grippers on at least one of the cylinders which are interconnected by said link means operated by said camming means, whereby said camming means operates said grippers at the line between the axes of the interconnected cylinders irrespective of the position of said link means.

11. A printing press according to claim 10 wherein said camming means comprises a pair of cams, one on each of said first and second link means, and wherein the grippers on each of said first means, diverting cylinder, turnover cylinder and the impression cylinder of the second printing unit are cam operated, said cams being adjustable with said first and second link means whereby the grippers operated thereby transfer sheets at the lines between the respective cylinders delivering and receiving sheets at the transfer points.

12. A printing press according to claim 11, including third link means maintaining constant the distance between the axes of the tensioning and turnover cylinders and wherein said third link means supports for movement therewith a cam for operating the tail edge gripper on the turnover cylinder.

13. A multicolor sheet fed printing press including a pair of printing units and a sheet transfer unit therebetween for turning sheets end for end whereby to print on a different side of each sheet at each unit, comprising:

a first impression cylinder at the first printing unit and having sheet grippers thereon, second impression cylinder at the second printing unit and having sheet grippers thereon, a first transfer cylinder having sheet grippers for receiving sheets printed on one side from the grippers of said first impression cylinder, a second transfer cylinder having sheet grippers for receiving sheets from said first transfer cylinder, carrying them past a transfer point in the rotation of said second transfer cylinder and releasing them as the tail of the sheet held thereby arrives at said transfer point, third transfer cylinder having first tail edge sheet grippers for receiving the tail edges of sheets from the second transfer cylinder and second tail edge grippers for receiving sheets from the first tail edge grippers and carrying them tail edge leading to the grippers on the second impression cylinder for transfer thereto, gears intergearing said first impression and transfer cylinder having gear teeth between the first impression cylinder and the first-transfer cylinder, said first and second transfer cylinders, and said transfer and second impression cylinders,

means maintaining the phase relationship of said first and second impression cylinders,

first means supporting the second transfer cylinder for arcuate adjustment about the axis of the first transfer cylinder, and

second" means supporting the third transfer cylinder for arcuate adjustment about the axis of the second impression cylinder, whereby said press is able to print sheets of varying lengths by retiming the receipt at said transfer point of the tail edges of sheets from the second transfer cylinder by the first tail edge grippers on the third transfer cylinder, said retiming being by means of said arcuate adjustment of said first and second supporting means, adjustment of said supporting means being ineffective to alter the phase relationship of the first and second impression cylinder.

14. A printing press according to claim 13 including means to maintain constant the distance between the axes of said second and third transfer cylinders.

15. A printing press according to claim 14 wherein the axes of the first transfer and second impression cylinders are fixed and comprise one bar of a four-bar linkage, and wherein the other three bars thereof consist of said first supporting means, said second supporting means and said distance maintaining means.

16. A printing press according to claim 15 wherein said other three bars of said four-bar linkage have supported thereon cams for operating the grippers on said first, second and third transfer cylinders and said second impression cylinder between their open and closed positions, said cams being movable with said other three bars to perform gripper opening and closing at the lines between the axes of each pair of interrelated adjacent cylinders.

17. A printing press according to claim 16 including a cam for opening the grippers on the second transfer cylinder at the time the tail edge of a sheet is taken at said transfer point by said first tail edge grippers, and means interconnecting said cam for coordinated adjustment in response to arcuate adjustment of said second transfer cylinder to open its grippers simultaneously with the closing of the first tail edge grippers on the third transfer cylinder.

18. A printing press according to claim 17 wherein said cam for opening the grippers on the second transfer cylinder is coaxial with the second transfer cylinder, and wherein said interconnecting means comprises a first gear segment provided in fixed relation to said cam and a second gear segment provided in fixed relation to said press.

19. In a sheet handling apparatus, a first cylinder having first means for gripping a sheet by a first edge of the sheet with the first edge leading, a downstream cylinder having second grippers to which said sheet is to be conveyeed turned over and with said first edge trailing and a second edge opposite said first edge leading, sheet turnover means for turning a sheet over intermediate said first cylinder and said downstream cylinder comprising a second cylinder defining a first sheet transfer nip with said first cylinder and a third cylinder defining a second sheet transfer nip with said downstream cylinder and a sheet transfer nip with said second cylinder, said sheet turnover means having sheet gripping means for receiving a sheet at said first transfer nip and transferring it to said downstream cylinder at said second sheet transfer nip including turnover additional gripping means on one of said second and third cylinders for gripping the trailing edge of a sheet on an adjacent one of said cylinders to take the sheet from the adjacent cylinder and to convey the sheet to an adjacent cylinder downstream with said second edge leading, and adjusting means for adjusting said second and third cylinders about the axis of said first and downstream cylinders while maintaining the sheet transfer nip therebetween to adjust the location of said first and second transfer nips to adjust the timing of of said sheet turnover means with the sheet grippers on said downstream cylinder for different length sheets.

20. In a printing press or other sheet handling machine having first and second stations for respectively receiving a sheet with a first edge of the sheet leading the sheet and with a second edge leading the sheet, said second edge being the edge which was trailing at the first station, sheet handling means for transferring the sheet from the first station to the second station comprising a first cylinder for handling the sheet with said first edge leading, a second cylinder defining a first sheet transfer nip with said first cylinder for transferring a sheet from the first cylinder to the second cylinder, a third cylinder for receiving a sheet from said second cylinder and defining a second sheet transfer nip therewith, a fourth sheet handling cylinder for receiving a sheet from said third cylinder and defining a third sheet transfer nip therewith, said cylinders being rotated in one direction and the adjacent surfaces of the adjacent one of said cylinders at said sheet transfer nips moving in the same direction with the relative phase of said adjacent cylinders determining the portions of the adjacent cylinders which meet at the sheet transfer nip, one of said second and third cylinders being a turnover cylinder and having gripper means comprising grippers for gripping the tail edge of a sheet on the one of said adjacent cylinders from which it receives a sheet provided the tail edge is at a predetermined position on said one of said adjacent cylinders, first, second, third and fourth drive gears on said first, second, third and fourth cylinders respectively, said drive gears being connected to their respective cylinders for movement therewith, the drive gear of said one of said second and third cylinders being free of mesh with the drive gear for the said adjacent cylinder for which it receives a sheet, each of said drive gears meshing with a cooperating driving gear, and means for changing the phase of said one cylinder with respect to said one of said adjacent cylinders to adjust said predetermined position on said one of said adjacent cylinders at which a sheet tail is to be gripped comprising mounting means for supporting said second and third cylinders for angular movement about the axis of said first and fourth cylinders respectively while maintaining a meshed relationship of said drive gears with their driving gears to thereby effect relative rotation of said one of said second and third cylinders and said one of said adjacent cylinders to adjust said sheet handling means for different sheet lengths.

21. In a printing press or other sheet handling machine as defined in claim 20 wherein each of said second and third cylinders have cams associated therewith for operating gripper means thereon, and said press further comprising means mounting said cams for movement with said second and third cylinders to maintain the proper operating relationship between said cams and said nips.

22. In a printing press or other sheet handling machine in claim 21 wherein said first and fourth cylinders have additional gripper operating cams associated therewith for operating grippers thereon at the respective nips for sheet transfer between said second and I third cylinders and means for adjusting said adjusting said additional operating cams on movement of said second and third cylinders to adjust for sheet length.

23. In a printing press or the like, a transfer unit comprising a plurality of cylinders each having a set of sheet gripper fingers thereon for successively transferring sheets from cylinder to cylinder,

each of said sets of fingers being operable between a closed condition in which they grasp sheets and an opened condition to release sheets,

each of said cylinders having means comprising a cam for operating said sets of fingers,

- each of said cams being non-rotatably fixed with respect to its cylinder during press operation and being located in positions whereby the grippers on the corresponding cylinder are operated for transferring sheets from cylinder to cylinderv on a line between the axes of two adjacent cylinders,

adjustment means for reorienting at least one of said cylinders in an arcuate path about the axis of a next adjacent cylinder, and

means mounting the said cam of said one and adjacent cylinders for arcuate movement on reorientation of said cylinder and connecting the cams to be operated by said adjusting means with said one cylinder on reorientation thereof to arcuately adjust the cams through the same angle whereby said lastnamed means maintains the cams in operative positions to effect sheet transfer on the line between the axes of the two cylinders for all adjusted positions of said one cylinder.

24. A transfer unit according to claim 23 wherein said one cylinder and the cylinder about the axis of which said one cylinder is adjusted comprise two of three cylinders of a sheet turnover unit which is located between two adjacent printing units of said press, and wherein said adjustment is made to accommodate sheets of different lengths which are turned end for end.

25. A multicolor sheet fed printing press including a pair of adjacent printing units and a sheet transfer unit between the printing units which is adapted to selectively present sheets from one unit to the next, either with the same edge leading whereby to print on the same sides of sheets at both units, or to turn sheets end for end whereby the tail edges of sheets leaving the first unit become the lead edges of sheets at the next unit in order to print on opposite sides of sheets at each unit, said sheet transfer unit comprising:

a first cylinder having sheet grippers for gripping sheets printed at the first printing unit,

a fourth cylinder having sheet grippers for receiving sheets directly from the grippers of said first cylinder when printing sheets on one side, the path of sheet travel over said first and fourth cylinders during printing on one side consitituting a first path,

a second cylinder having sheet grippers for receiving sheets from the grippers of said first cylinder when printing sheets on opposite sides,

a third cylinder having sheet grippers for receiving sheets from said second cylinder and transferring them to said fourth cylinder when printing sheets on opposite sides, the path of sheet travel over said second and third cylinders during printing on opposite sides of sheets constituting a second path,

means for turning sheets over and end for end while traveling in said second path comprising turnover means on at least one of said second and third cylinders,

means for operating said grippers to transfer sheets either along said first or second path,

one of said cylinders including means for causing sheets carried thereby to lie in intimate contact with its periphery and said grippers on the next successive cylinder for receiving sheets during printing on opposite sides to receive the tail ends of sheets from said one cylinder as the lead edge of the sheet,

means intergearing all of said four cylinders with the adjacent cylinders except at the line between said one cylinder against which sheets lie in intimate,

contact and the next successive cylinder for receiving the tail ends of sheets, and means mounting said one cylinder for arcuate adjustment about its immediately preceeding cylinder and for mounting said successive cylinder for arcuate adjustment about its next following cylinder for accommodating said cylinders to handle sheets of different lengths while traveling along said second path. 26. A printing press according to claim 25 including means for maintaining constant the distance between the axes of said one cylinder and said next successive cylinder for various positions of adjustment thereof.

27. A printing press according to claim 25 wherein the mounting for arcuate adjustment of at least one of said one cylinder and said next successive cylinder includes a link, and wherein cams are mounted on said link for operating the grippers on those cylinders connected by said link, whereby the cams operate the grippers on the line between centers of those cylinders irrespective of the positions to which adjusted;

28. A printing press according to claim 25 wherein link means interconnects said first and second, said second and third and said third and fourth cylinders, and wherein said first and fourth cylinders are mounted on fixed axes, said link means and the fixed axes comprising a four-bar linkage which enables adjustment of said second cylinder relative to the first, said third cylinder relative to the second, and said fourth cylinder relative to said third cylinder.

29. A printing press according to claim 28 including means for adjusting said second and third cylinders and said link means, and means for locking said adjusting means relative to a fixed portion of said press.

30. In a printing press having first sheet handling means comprising at least one sheet handling cylinder for transferring a sheet along a first sheet transfer path from a first station to a second station with a first edge leading and a second edge trailing, the method of transferring a sheet to the second station with the second edge leading and the sheet turned over comprising the steps of diverting the sheet from said first path while gripping the first edge of the sheet with a first gripper moving continuously in one direction in a first circular path about an axis, continuously rotating a second gripper in one direction in a circular path adjacent the first circular path of the first gripper to grip at a first nip the said second edge of a sheet being carried by the first gripper while the second gripper is moving in the same direction and speed as the sheet tail, and continuing the movement of the second gripper in said one direction in its circular path to convey the sheet from the first circular path into the second circular path with the second edge leading, and transferring the sheet from said second gripper to a third gripper rotating about an axis for transferring sheets along said first path for transfer to said second station with the second edge leading the sheet, and moving the path of said second gripper means about one of said axes to adjust the phase of the machine at which the second gripper arrives at the first nip to grip the trailing edge of the sheet.

31. A multicolor sheet-fed printing press including a pair of adjacent first and second printing units and a sheet transfer unit between the printing units which is adapted to selectively present sheets from one unit to the next, either with the same edge leading whereby to print on the same sides of sheets at both units, or to turn sheets end for end whereby the tail edges of sheets leaving the first unit becomes the lead edges of sheets at the next unit in order to print on different sides of the sheets at said units, said sheet transfer unit comprising:

a first rotatable cylinder,

a sheet handling cylinder defining a first transfer nip with said first cylinder with said cylinders running at the same surface speed and having their surfaces traveling in the same direction and in close proximity at said first transfer nip,

a tail turnover cylinder running in close proximity to said sheet handling cylinder and at the same surface speed to define therewith a second transfer nip where the surfaces of the cylinders are moving in the same direction,

a fourth cylinder running at the same surface speed in close proximity to said turnover cylinder to define a third transfer nip on one hand and in close proximity to said first cylinder to define a fourth transfer nip on the other hand with the adjacent cylinder surfaces at said nips traveling in the same direction and at the same surface speed,

first grippers on said cylinders for sequentially moving sheets in register through said first nip, around a portion of the first cylinder and through said fourth nip while maintaining their leading edges forward for presentation to the second printing unit for printing sheets on the same sides at both units,

second means for moving sheets entering said first nip through and beyond said second nip and continuing around a portion of said sheet handling cylinder,

means on said turnover cylinder for gripping the tail ends of sheets carried by said sheet handling cylinder at said second nip to reverse the sheet and make their trailing ends lead,

means on said fourth cylinder for receiving sheets from the gripping means on said turnover cylinder at said third nip and moving them through said fourth nip with their former trailing ends forward for presentation to the second unit for printing sheets on the reverse sides at the second unit,

and means for accurately adjusting said sheet handling cylinder about the axis of the first cylinder and the turnover cylinder about the axis of the fourth cylinder for accommodating sheet handling sheets of different lengths when printing on opposite sides.

32. A printing press according to claim 31 further including means maintaining the axes of said sheet handling diverting and turnover cylinders constant for all positions of adjustment.

33. In a printing press for selectively printing sheets on one side only or perfecting by printing on opposite sides, said press comprising a pair of adjacent first and second printing units with respective printing nips, means for moving sheets from the printing nip of the first limit with a first edge leading through a first transfer nip and along a portion of a cylindrical path and to and through a fourth transfer nip for presentation to said second printing unit, means for receiving at said first transfer nip the said first edges of sheets in said cylindrical path and for moving the sheets around a portion of a second cylindrical path diverging from said first cylindrical path and separate from the path to and through said fourth transfer nip and moving the sheets beyond a second transfer nip, means for grasping sheets in said second cylindrical path by their tail ends at said second transfer nip and moving their tail ends initially in the same general direction as the second cylindrical path but along a third cylindrical path diverging from said second cylindrical path and for presenting the tail ends of the sheets as the leading edge thereof at a third transfer nip, the last said means defining a said third transfer nip at a fourth cylindrical path different from said first cylindrical path with said fourth cylindrical path defining said fourth transfer nip in part and means operating in said fourth cylindrical path to receive the leading edge of sheets at said third and fourth transfer nips respectively and forward them for presentation to cylinder from which said turnover gripping means takes a sheet are relatively rotatable during movement of said second and third cylinders about said first and downstream cylinders to adjust the phase thereof relative to each other and said sheet handling machine comprises means for effecting said relative rotation of said one of said second and third cylinders in response to said relative movement of said second and third cylinders about the axis of said first and downstream cylinders respectively.

U M'ltl n STATES PATENT OFFMI 2"; CERTIMCATE 0i CUHRECHQN Patent No. 3,884,146 Dat d May 20, 1975 Inventor) Rudolph H, Ruetschle Page 1 of 5 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 1, after line 14, insert,

-said sheet transfer means comprising first means having gripping Q means for gripping and receiving the lead edges of sheets from the grippers of the first impression cylinder and transporting them along a first path for presentation of the lead edges to Q the grippers on the second impression cylinder at a first sheet transfer location, means supporting said first means for circular rotation, second means out of said first path having a lead-edge grippers for receiving the lead edges of sheets as printed at said first printing nip and for turning the sheets over and end for end to make the tail edges become the lead edges and for transporting the sheets with their former tail edges forward along a second path different from said first Q path for presentation to the grippers on the second impression cylinder, means supporting the grippers of said second means for rotation in a circular path, said second means comprising 

1. A multicolor sheet-fed printing press including first and second adjacent printing units providing first and second printing nips respectively, each unit comprising an impression cylinder with gripper fingers thereon, and sheet transfer means between the printing units for transferring sheets from the first unit to the second unit and selectively presenting the sheets to the second printing nips either with the same edge leading as was leading in the first printing nip whereby to print on the same sides of sheets at both units, or to turn sheets over and end for end whereby the tail edges of sheets leaving the first printing nip become the lead edges of sheets at the next unit in order to print on opposite sides of sheets at each unit,
 2. A printing press according to claim 1 including means maintaining constant the distance between the axes of the diverting and turnover cylinders throughout their full range of adjustment.
 3. A printing press according to claim 1 including a cam for opening the lead edge grippers on the diverting cylinder at the time sheets are taken by the tail edge grippers on the turnover cylinder, and means interconnecting said lead edge gripper cam for coordinated adjustment in response to arcuate adjustment of said turnover cylinder, whereby said cam is adapted to operate the lead edge grippers on the diverting cylinder to their opened condition when the tails of sheets held thereby are taken by the tail edge grippers, irrespective of the adjusted position of said diverting cylinder.
 4. A printing press according to claim 3 wherein said diverting cylinder lead edge gripper cam is pivotally mounted with respect to the axis of the diverting cylinder, a first gear segment fixed relative to said cam, and a second Gear segment fixed relative to said press and coaxial with said sheet handling cylinder of said first means, whereby arcuate adjustment of said diverting cylinder rocks said cam to a new position in response to meshing teeth of said first and second gear segments.
 5. A printing press according to claim 1 wherein the meshing relationship of the gearing of the first means with the gears on the impression cylinders of the first and second printing units and the phase relationship of the respective cylinders are maintained intact throughout the full range of arcuate adjustment of said diverting and turnover cylinders.
 6. A printing press according to claim 5 wherein said distance maintaining means comprises at least one link connected at its ends to said turnover and diverting cylinders at their respective axes.
 7. A printing press according to claim 5 including first link means supporting said diverting cylinder for the arcuate adjustment about the axis of said cylinder of said first means, and second link means for supporting said turnover cylinder for the arcuate adjustment about the axis of the impression cylinder of the second printing unit.
 8. A printing press according to claim 7 including third link means maintaining constant the distance between the axes of the diverting and turnover cylinders, said first, second and third link means together with the fixed axes for said cylinder of said first means and the impression cylinder of the second printing unit comprising a four-bar linkage.
 9. A printing press according to claim 8 wherein means is provided for locking the four-bar linkage in a fixed position during operation of said press, and means interconnecting a fixed press member and said linkage for adjusting said linkage.
 10. A printing press according to claim 7 including camming means for performing camming operations mounted on at least one of said first and second link means, and means for operating the grippers on at least one of the cylinders which are interconnected by said link means operated by said camming means, whereby said camming means operates said grippers at the line between the axes of the interconnected cylinders irrespective of the position of said link means.
 11. A printing press according to claim 10 wherein said camming means comprises a pair of cams, one on each of said first and second link means, and wherein the grippers on each of said first means, diverting cylinder, turnover cylinder and the impression cylinder of the second printing unit are cam operated, said cams being adjustable with said first and second link means whereby the grippers operated thereby transfer sheets at the lines between the respective cylinders delivering and receiving sheets at the transfer points.
 12. A printing press according to claim 11, including third link means maintaining constant the distance between the axes of the tensioning and turnover cylinders and wherein said third link means supports for movement therewith a cam for operating the tail edge gripper on the turnover cylinder.
 13. A multicolor sheet fed printing press including a pair of printing units and a sheet transfer unit therebetween for turning sheets end for end whereby to print on a different side of each sheet at each unit, comprising: a first impression cylinder at the first printing unit and having sheet grippers thereon, a second impression cylinder at the second printing unit and having sheet grippers thereon, a first transfer cylinder having sheet grippers for receiving sheets printed on one side from the grippers of said first impression cylinder, a second transfer cylinder having sheet grippers for receiving sheets from said first transfer cylinder, carrying them past a transfer point in the rotation of said second transfer cylinder and releasing them as the tail of the sheet held thereby arrives at said transfer point, a third transfer cylinder having first tail edge sheet grippers for receiving the tail edges of sheEts from the second transfer cylinder and second tail edge grippers for receiving sheets from the first tail edge grippers and carrying them tail edge leading to the grippers on the second impression cylinder for transfer thereto, gears intergearing said first impression and transfer cylinder having gear teeth between the first impression cylinder and the first transfer cylinder, said first and second transfer cylinders, and said transfer and second impression cylinders, means maintaining the phase relationship of said first and second impression cylinders, first means supporting the second transfer cylinder for arcuate adjustment about the axis of the first transfer cylinder, and second means supporting the third transfer cylinder for arcuate adjustment about the axis of the second impression cylinder, whereby said press is able to print sheets of varying lengths by retiming the receipt at said transfer point of the tail edges of sheets from the second transfer cylinder by the first tail edge grippers on the third transfer cylinder, said retiming being by means of said arcuate adjustment of said first and second supporting means, adjustment of said supporting means being ineffective to alter the phase relationship of the first and second impression cylinder.
 14. A printing press according to claim 13 including means to maintain constant the distance between the axes of said second and third transfer cylinders.
 15. A printing press according to claim 14 wherein the axes of the first transfer and second impression cylinders are fixed and comprise one bar of a four-bar linkage, and wherein the other three bars thereof consist of said first supporting means, said second supporting means and said distance maintaining means.
 16. A printing press according to claim 15 wherein said other three bars of said four-bar linkage have supported thereon cams for operating the grippers on said first, second and third transfer cylinders and said second impression cylinder between their open and closed positions, said cams being movable with said other three bars to perform gripper opening and closing at the lines between the axes of each pair of interrelated adjacent cylinders.
 17. A printing press according to claim 16 including a cam for opening the grippers on the second transfer cylinder at the time the tail edge of a sheet is taken at said transfer point by said first tail edge grippers, and means interconnecting said cam for coordinated adjustment in response to arcuate adjustment of said second transfer cylinder to open its grippers simultaneously with the closing of the first tail edge grippers on the third transfer cylinder.
 18. A printing press according to claim 17 wherein said cam for opening the grippers on the second transfer cylinder is coaxial with the second transfer cylinder, and wherein said interconnecting means comprises a first gear segment provided in fixed relation to said cam and a second gear segment provided in fixed relation to said press.
 19. In a sheet handling apparatus, a first cylinder having first means for gripping a sheet by a first edge of the sheet with the first edge leading, a downstream cylinder having second grippers to which said sheet is to be conveyeed turned over and with said first edge trailing and a second edge opposite said first edge leading, sheet turnover means for turning a sheet over intermediate said first cylinder and said downstream cylinder comprising a second cylinder defining a first sheet transfer nip with said first cylinder and a third cylinder defining a second sheet transfer nip with said downstream cylinder and a sheet transfer nip with said second cylinder, said sheet turnover means having sheet gripping means for receiving a sheet at said first transfer nip and transferring it to said downstream cylinder at said second sheet transfer nip including turnover additional gripping means on one of said second and third cylinders for gripping the trailing edge of a sheet on an adjacent One of said cylinders to take the sheet from the adjacent cylinder and to convey the sheet to an adjacent cylinder downstream with said second edge leading, and adjusting means for adjusting said second and third cylinders about the axis of said first and downstream cylinders while maintaining the sheet transfer nip therebetween to adjust the location of said first and second transfer nips to adjust the timing of of said sheet turnover means with the sheet grippers on said downstream cylinder for different length sheets.
 20. In a printing press or other sheet handling machine having first and second stations for respectively receiving a sheet with a first edge of the sheet leading the sheet and with a second edge leading the sheet, said second edge being the edge which was trailing at the first station, sheet handling means for transferring the sheet from the first station to the second station comprising a first cylinder for handling the sheet with said first edge leading, a second cylinder defining a first sheet transfer nip with said first cylinder for transferring a sheet from the first cylinder to the second cylinder, a third cylinder for receiving a sheet from said second cylinder and defining a second sheet transfer nip therewith, a fourth sheet handling cylinder for receiving a sheet from said third cylinder and defining a third sheet transfer nip therewith, said cylinders being rotated in one direction and the adjacent surfaces of the adjacent one of said cylinders at said sheet transfer nips moving in the same direction with the relative phase of said adjacent cylinders determining the portions of the adjacent cylinders which meet at the sheet transfer nip, one of said second and third cylinders being a turnover cylinder and having gripper means comprising grippers for gripping the tail edge of a sheet on the one of said adjacent cylinders from which it receives a sheet provided the tail edge is at a predetermined position on said one of said adjacent cylinders, first, second, third and fourth drive gears on said first, second, third and fourth cylinders respectively, said drive gears being connected to their respective cylinders for movement therewith, the drive gear of said one of said second and third cylinders being free of mesh with the drive gear for the said adjacent cylinder for which it receives a sheet, each of said drive gears meshing with a cooperating driving gear, and means for changing the phase of said one cylinder with respect to said one of said adjacent cylinders to adjust said predetermined position on said one of said adjacent cylinders at which a sheet tail is to be gripped comprising mounting means for supporting said second and third cylinders for angular movement about the axis of said first and fourth cylinders respectively while maintaining a meshed relationship of said drive gears with their driving gears to thereby effect relative rotation of said one of said second and third cylinders and said one of said adjacent cylinders to adjust said sheet handling means for different sheet lengths.
 21. In a printing press or other sheet handling machine as defined in claim 20 wherein each of said second and third cylinders have cams associated therewith for operating gripper means thereon, and said press further comprising means mounting said cams for movement with said second and third cylinders to maintain the proper operating relationship between said cams and said nips.
 22. In a printing press or other sheet handling machine in claim 21 wherein said first and fourth cylinders have additional gripper operating cams associated therewith for operating grippers thereon at the respective nips for sheet transfer between said second and third cylinders and means for adjusting said adjusting said additional operating cams on movement of said second and third cylinders to adjust for sheet length.
 23. In a printing press or the like, a transfer unit comprising a plurality of cylinders each having a set of sheet gripper fingers thereoN for successively transferring sheets from cylinder to cylinder, each of said sets of fingers being operable between a closed condition in which they grasp sheets and an opened condition to release sheets, each of said cylinders having means comprising a cam for operating said sets of fingers, each of said cams being non-rotatably fixed with respect to its cylinder during press operation and being located in positions whereby the grippers on the corresponding cylinder are operated for transferring sheets from cylinder to cylinder on a line between the axes of two adjacent cylinders, adjustment means for reorienting at least one of said cylinders in an arcuate path about the axis of a next adjacent cylinder, and means mounting the said cam of said one and adjacent cylinders for arcuate movement on reorientation of said cylinder and connecting the cams to be operated by said adjusting means with said one cylinder on reorientation thereof to arcuately adjust the cams through the same angle whereby said last-named means maintains the cams in operative positions to effect sheet transfer on the line between the axes of the two cylinders for all adjusted positions of said one cylinder.
 24. A transfer unit according to claim 23 wherein said one cylinder and the cylinder about the axis of which said one cylinder is adjusted comprise two of three cylinders of a sheet turnover unit which is located between two adjacent printing units of said press, and wherein said adjustment is made to accommodate sheets of different lengths which are turned end for end.
 25. A multicolor sheet fed printing press including a pair of adjacent printing units and a sheet transfer unit between the printing units which is adapted to selectively present sheets from one unit to the next, either with the same edge leading whereby to print on the same sides of sheets at both units, or to turn sheets end for end whereby the tail edges of sheets leaving the first unit become the lead edges of sheets at the next unit in order to print on opposite sides of sheets at each unit, said sheet transfer unit comprising: a first cylinder having sheet grippers for gripping sheets printed at the first printing unit, a fourth cylinder having sheet grippers for receiving sheets directly from the grippers of said first cylinder when printing sheets on one side, the path of sheet travel over said first and fourth cylinders during printing on one side consitituting a first path, a second cylinder having sheet grippers for receiving sheets from the grippers of said first cylinder when printing sheets on opposite sides, a third cylinder having sheet grippers for receiving sheets from said second cylinder and transferring them to said fourth cylinder when printing sheets on opposite sides, the path of sheet travel over said second and third cylinders during printing on opposite sides of sheets constituting a second path, means for turning sheets over and end for end while traveling in said second path comprising turnover means on at least one of said second and third cylinders, means for operating said grippers to transfer sheets either along said first or second path, one of said cylinders including means for causing sheets carried thereby to lie in intimate contact with its periphery and said grippers on the next successive cylinder for receiving sheets during printing on opposite sides to receive the tail ends of sheets from said one cylinder as the lead edge of the sheet, means intergearing all of said four cylinders with the adjacent cylinders except at the line between said one cylinder against which sheets lie in intimate contact and the next successive cylinder for receiving the tail ends of sheets, and means mounting said one cylinder for arcuate adjustment about its immediately preceeding cylinder and for mounting said successive cylinder for arcuate adjustment about its next following cylinder for accommodating said cylinders to handle sheets of diffeRent lengths while traveling along said second path.
 26. A printing press according to claim 25 including means for maintaining constant the distance between the axes of said one cylinder and said next successive cylinder for various positions of adjustment thereof.
 27. A printing press according to claim 25 wherein the mounting for arcuate adjustment of at least one of said one cylinder and said next successive cylinder includes a link, and wherein cams are mounted on said link for operating the grippers on those cylinders connected by said link, whereby the cams operate the grippers on the line between centers of those cylinders irrespective of the positions to which adjusted.
 28. A printing press according to claim 25 wherein link means interconnects said first and second, said second and third and said third and fourth cylinders, and wherein said first and fourth cylinders are mounted on fixed axes, said link means and the fixed axes comprising a four-bar linkage which enables adjustment of said second cylinder relative to the first, said third cylinder relative to the second, and said fourth cylinder relative to said third cylinder.
 29. A printing press according to claim 28 including means for adjusting said second and third cylinders and said link means, and means for locking said adjusting means relative to a fixed portion of said press.
 30. In a printing press having first sheet handling means comprising at least one sheet handling cylinder for transferring a sheet along a first sheet transfer path from a first station to a second station with a first edge leading and a second edge trailing, the method of transferring a sheet to the second station with the second edge leading and the sheet turned over comprising the steps of diverting the sheet from said first path while gripping the first edge of the sheet with a first gripper moving continuously in one direction in a first circular path about an axis, continuously rotating a second gripper in one direction in a circular path adjacent the first circular path of the first gripper to grip at a first nip the said second edge of a sheet being carried by the first gripper while the second gripper is moving in the same direction and speed as the sheet tail, and continuing the movement of the second gripper in said one direction in its circular path to convey the sheet from the first circular path into the second circular path with the second edge leading, and transferring the sheet from said second gripper to a third gripper rotating about an axis for transferring sheets along said first path for transfer to said second station with the second edge leading the sheet, and moving the path of said second gripper means about one of said axes to adjust the phase of the machine at which the second gripper arrives at the first nip to grip the trailing edge of the sheet.
 31. A multicolor sheet-fed printing press including a pair of adjacent first and second printing units and a sheet transfer unit between the printing units which is adapted to selectively present sheets from one unit to the next, either with the same edge leading whereby to print on the same sides of sheets at both units, or to turn sheets end for end whereby the tail edges of sheets leaving the first unit becomes the lead edges of sheets at the next unit in order to print on different sides of the sheets at said units, said sheet transfer unit comprising: a first rotatable cylinder, a sheet handling cylinder defining a first transfer nip with said first cylinder with said cylinders running at the same surface speed and having their surfaces traveling in the same direction and in close proximity at said first transfer nip, a tail turnover cylinder running in close proximity to said sheet handling cylinder and at the same surface speed to define therewith a second transfer nip where the surfaces of the cylinders are moving in the same direction, a fourth cylinder running at the same surface speed in close proximity to Said turnover cylinder to define a third transfer nip on one hand and in close proximity to said first cylinder to define a fourth transfer nip on the other hand with the adjacent cylinder surfaces at said nips traveling in the same direction and at the same surface speed, first grippers on said cylinders for sequentially moving sheets in register through said first nip, around a portion of the first cylinder and through said fourth nip while maintaining their leading edges forward for presentation to the second printing unit for printing sheets on the same sides at both units, second means for moving sheets entering said first nip through and beyond said second nip and continuing around a portion of said sheet handling cylinder, means on said turnover cylinder for gripping the tail ends of sheets carried by said sheet handling cylinder at said second nip to reverse the sheet and make their trailing ends lead, means on said fourth cylinder for receiving sheets from the gripping means on said turnover cylinder at said third nip and moving them through said fourth nip with their former trailing ends forward for presentation to the second unit for printing sheets on the reverse sides at the second unit, and means for accurately adjusting said sheet handling cylinder about the axis of the first cylinder and the turnover cylinder about the axis of the fourth cylinder for accommodating sheet handling sheets of different lengths when printing on opposite sides.
 32. A printing press according to claim 31 further including means maintaining the axes of said sheet handling diverting and turnover cylinders constant for all positions of adjustment.
 33. In a printing press for selectively printing sheets on one side only or perfecting by printing on opposite sides, said press comprising a pair of adjacent first and second printing units with respective printing nips, means for moving sheets from the printing nip of the first limit with a first edge leading through a first transfer nip and along a portion of a cylindrical path and to and through a fourth transfer nip for presentation to said second printing unit, means for receiving at said first transfer nip the said first edges of sheets in said cylindrical path and for moving the sheets around a portion of a second cylindrical path diverging from said first cylindrical path and separate from the path to and through said fourth transfer nip and moving the sheets beyond a second transfer nip, means for grasping sheets in said second cylindrical path by their tail ends at said second transfer nip and moving their tail ends initially in the same general direction as the second cylindrical path but along a third cylindrical path diverging from said second cylindrical path and for presenting the tail ends of the sheets as the leading edge thereof at a third transfer nip, the last said means defining a said third transfer nip at a fourth cylindrical path different from said first cylindrical path with said fourth cylindrical path defining said fourth transfer nip in part and means operating in said fourth cylindrical path to receive the leading edge of sheets at said third and fourth transfer nips respectively and forward them for presentation to the printing nip of said second printing unit, and means for varying the positions of said first, second and third transfer nips to adjust the printing press to perfect sheets of different lengths.
 34. A printing press according to claim 33 including mean for varying the distance between the first and second transfer nips to adjust for perfecting sheets of different lengths.
 35. In a sheet handling apparatus as defined in claim 34 wherein said one of said second and third cylinders having said turnover gripping means thereon and the cylinder from which said turnover gripping means takes a sheet are relatively rotatable during movement of said second and third cylinders about said first and downstream cylinders to adjust the phase thereof relatIve to each other and said sheet handling machine comprises means for effecting said relative rotation of said one of said second and third cylinders in response to said relative movement of said second and third cylinders about the axis of said first and downstream cylinders respectively. 